Prevention of thiourea-induced pulmonary edema by hydroxyl-radical scavengers

Thiourea (TU), a very effective hydroxyl radical (.OH) scavenger, has little value as a probe of .OH in vivo because it causes fatal pulmonary edema. To test the hypothesis that TU-induced lung injury results from .OH-mediated oxidation of TU to toxic cyanamide, we pretreated rats with .OH scavengers, dimethylsulfoxide (DMSO), ethanol, and mannitol, prior to treatment with TU (3 mg/kg), preventing 91, 63, and 53%, respectively, of increases in lung weight to body weight ratios and 93, 67, and 46% of increases in lung lavage albumin concentrations. Furthermore, treatment of rats with cyanamide (CYN) (100 mg/kg) also caused increases in lung weight to body weight ratios (CYN: 7.39 +/- 0.57 X 10(-3) vs. controls: 5.46 +/- 0.26). N,N'-dimethylation of TU (DMTU) prevented TU toxicity, because treatment with DMTU did not significantly increase lung weight to body weight ratios (DMTU: 5.12 +/- 0.16 X 10(-3) vs. controls: 5.46 +/- 0.26) or lung lavage albumin (DMTU: 14 +/- 1 mg/100 ml vs. controls: 11 +/- 1). DMTU remained a very effective in vivo .OH scavenger, increasing survival of lethally irradiated mice treated with 600 mg/kg DMTU to 79% compared with 8% in untreated controls.